The present invention relates to a process for preparing a catalyst system for the polymerization of olefins, which comprises initially charging one or more compounds of the formula I a or I b, 
where the variables are defined as follows:
M is a transition metal of groups 5 to 10 of the Periodic Table of the Elements,
A is selected from among N, P and As,
Axe2x80x2 is selected from among O and S,
Nu1, Nu2 are N or P,
X1, X2 are halogen or C1-C4-alkoxy;
R1, R2 are unsubstituted or substituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl, C6-C14-aryl or five- or six-membered N-containing heteroaryl,
R3, R4 are hydrogen, unsubstituted or substituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl, C6-C14-aryl or five- or six-membered N-containing heteroaryl,
R5 to R7 are each selected independently from among hydrogen, unsubstituted or substituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl, C6-C14-aryl and five- and six-membered N-containing heteroaryl, halogen, C1-C6-alkoxy, NO2, SiR8R9R10 and OSiR8R9R10 where adjacent radicals together with the parent heteroaryl may form a 5- to 10-membered ring,
R8 to R10 are selected independently from among hydrogen and substituted or unsubstituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl and C6-C14-aryl; then adding a molecularly defined activator of the formulae II a to c
[(Lxe2x80x94H)]+[(Mxe2x80x2)Q1Q2Q3Q4]xe2x88x92xe2x80x83xe2x80x83II a
xe2x80x83[(CAr3)]+[(Mxe2x80x2)Q1Q2Q3Q4]xe2x88x92xe2x80x83xe2x80x83II b
[(Mxe2x80x2)Q1Q2Q3]xe2x80x83xe2x80x83II c
where the radicals have the following meanings:
[Lxe2x80x94H]+ is a Brxc3x8nsted acid, where L is an electron-neutral Lewis base,
Mxe2x80x2 is an element of group 13 of the Periodic Table of the elements,
Q1 to Q4 are selected independently from among hydride, unsubstituted or substituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl, C6-C14-aryl and halide, with the proviso that not more than two radicals Q1 and Q2 are halide;
Ar are identical or different and are selected from among unsubstituted or substituted C6-C14-aryl,
and finally adding an alkylating agent selected from among LiR11, MgR11R12 and AlR12R13R14, where
R11 to R14 are selected independently from among unsubstituted or substituted C1-C12-alkyl, C3-C12-cycloalkyl, C7-C15-aralkyl and C6-C14-aryl.
The present invention also provides the catalyst system prepared by the abovementioned process and provides a process for the polymerization and copolymerization of olefins using this catalyst system.